The present invention relates generally to tractor frames and, more particularly, to telescopic tractor frames which act to increase or decrease the wheel base of a tractor.
Modern tractors have various features designed for different applications. Pulling or carrying large loads generally requires either counter-balanced tractors or tractors which longer wheel bases. Counter-balanced tractors have the disadvantage of increased fuel consumption, increased tire wear and additional ground compaction while tractors with longer wheel bases have the disadvantage of decreased maneuverability. Tractors with shorter wheel bases have the disadvantages of a smaller load capacity as well as decreased ground following ability when working in a field. Additionally, neither long nor short wheel based tractors work well on extremely uneven ground or very muddy or boggy ground. Furthermore, it is neither time nor cost efficient to switch between long and short wheel based tractors for different applications.
Accordingly, it is desirable to provide a four-wheel-drive tractor with a telescopic tractor frame. It is also desirable to provide a tractor with a frame which swivels to keep all four wheels in contact with the ground.
A number of attempts have been made to provide a vehicle with a telescopic frame. These telescopic frames usually have some very particular application and are generally not suitable for other more general applications.
U.S. Pat. No. 4,611,683 discloses a farm tractor with a telescoping frame. However, the telescopic frame shown in this patent is designed merely to allow the operator to drive the tractor over an implement to hitch the implement to the center of the tractor. The tractor's longitudinal extension is not suitable for increasing load handling capabilities nor to extricating the tractor from muddy or boggy terrain.
Likewise, none of the prior art devices disclose a longitudinally telescopic tractor frame suitable for use in extricating the vehicle from muddy or boggy situations while allowing the back axis to rotate longitudinally in relationship to the front axis.
The difficulties in the prior art longitudinally telescopic frames are substantially eliminated by the present invention.